The starting products or prepolymers or resins which are within the scope of the present invention are liquid or plastic before and during the processing and shaping processes. Following the traditional shaping and processing, as a result of polyreaction (polymerization, poly-condensation, polyaddition), yields thermosetting plastics. A three-dimensional, crosslinked, hard, non-melting resin, the thermosetting plastic, is obtained by the polyreaction, and the thermosetting plastic thus differs basically from traditional the thermoplastic which can be liquified and/or plasticized repeatedly by reheating.
As a result of the very high density of crosslinking, the crosslinked reaction resins have a number of valuable properties, which provide the reason that they, along with the thermoplastics, are the most used polymers. These valuable properties especially include hardness, strength, chemical resistance and temperature durability. Because of these properties, these reaction resins are used for various purposes, for instance for the production of fiber-reinforced plastics, for insulation materials used in electrotechnology, for the production of structural adhesives, laminated plastics, annealing lacquers, coatings and the like.
In addition to these advantageous properties, thermosetting plastics have one serious drawback, which in many cases prevents their use. As a result of the highly crosslinked state, they are very brittle and have a low impact resistance. This appears especially in the range of low temperatures, in other words at temperatures below 0° C., so that, for uses wherein the polymer is to be subjected to high mechanical stresses at low temperatures, especially impact stresses, the thermoplastic polymers generally have the advantage, whereby the drawbacks connected therewith, such as lower heat deformation resistance and chemical resistance, must be taken into consideration.
Since this drawback is not particularly favorable, there have been many attempts in the past to improve the impact resistance or flexibility of thermosetting plastics. Thus, it is already known, for instance, to mix reaction resins with fiber fillers, in order to increase the impact resistance. The improvements which are thus obtained are nonetheless quite limited. The addition to resins of powdered, soft filler material, such as powdered rubber or soft elastic plastic powder, is also known. The particle dimensions of such powdered additives is in the range of approximately 0.04 to 1 mm, which obviously does not suffice to improve such reaction resins to the desired degree, and which therefore enhance the drawbacks relative to other important properties required for technical use of this sort of modified thermosetting plastic.
Attempts have been made to improve the impact resistance of cross-linked reaction resins by addition of softeners. The added softeners do not react with the reaction resin, but rather as a result of layering, cause a widening of the network of thermosetting plastics and with that a certain softening of the material. A remarkable improvement of the impact resistance can actually be attained in this manner, which however unfortunately results in a limitation of the outlay which is required for the quality of other essential features of the thermosetting plastics.
Therefore, with the use of softeners, a latent danger exists of migration occurring following the cross-linking of the reaction resin or with further aging, with the negative results inherent therein for the surface properties of the material, such as the adherence, spreadability, polish and the like.
Furthermore, attempts have also been made to increase the elasticity of thermosetting plastics, in that chain lengtheners are added, which are incorporated into the network with the hardening process and lower the density of cross-linking Epoxy resins for instance could be elasticized according to this principle by addition of epoxidized soybean oil, dimeric fatty acids or epoxy-functional polyglycol ethers. Since the improvement in elasticity, however, is attained by a decrease of the cross-linking density, desirable properties such as hardness, chemical resistance or temperature durability are affected. This solution therefore has led to results which were not totally satisfactory.
It is also known to use liquid or solid, but uncross-linked butadiene-acrylonitrile rubbers (nitrile rubber, NBR) as additives to improve the viscosity of the reaction resins. These nitrile rubbers contain functional groups which can be reacted with the reaction resin with the cross-linking process or even in a previous reaction. The remarkable feature of these modifiers as compared with those cited as being used until now resides in that they are actually miscible with the uncross-linked reaction resin, and a phase separation nonetheless takes place during the cross-linking of the reaction resin, in which the rubber phase is deposited in the form of fine droplets. As a result of the reaction of the functional groups located on the surface of the nitrile rubber particles with the reaction resin, a solid connection of the rubber phase with the thermosetting plastic matrix is formed.
This type of modification of reaction resins is actually more advantageous because the effect is attained not by simply lowering the network density, but rather by formation of a separate soft phase with the result that the other advantageous properties of the thermosetting plastics are not influenced quantitatively by the modifier, as is the case with the measures which were formerly used. Unfortunately, however, such thermosetting plastics modified with nitrile rubber have notable problems. For instance, the heat resistance of thermosetting plastics modified with nitrile rubber is notably decreased and because of that, their capacity for use at high temperatures is questionable. This is also true of many electric properties, such as for example the dielectric strength or breakdown resistance. Because of the relatively good compatibility of the nitrile rubber with most reaction resins, especially with epoxy resins, a certain portion of the rubber does not participate in the phase separation during the cross-linking and is incorporated into the resin matrix. The density of the cross-linked reaction resin is thereby lowered with the already noted negative results for the configuration of the properties of the completed thermosetting plastics. Another drawback is the very high viscosity of the nitrile-rubber modifiers, which leads to processing problems and which negatively influences the flow properties of the modified reaction resin
Additionally, it is known that epoxy resins contain a number of the reactive oxirane ring structures commonly called “epoxy.” The most commonly used resins are derivatives of bisphenol A and epichlorohydrin shown in structure below. However, other types of resins (for example bisphenol F type) are also common to achieve various properties.

Epoxy coatings are formed by the reaction of a poly(epoxide)-based oligomer or resin with a polyfunctional active hydrogen compound hardener or curing agent. This curing reaction crosslinks the epoxy resin polymer and solidifies it into a durable coating. The focus of this invention is two component or 2K systems, with separate epoxy and polyamine hardeners (a polyamine pre-reacted with some epoxy or dimer fatty acid curing agent).
Organic solvents have been used to manage viscosity and maintain compatibility between the epoxy resin and hardener components, but are VOCs. Water use is more environmentally friendly, but requires surfactants since epoxy resins are hydrophobic and water reactive and therefore incompatible with water.
Epoxy resins are also available in various molecular weights to provide unique properties to the final coating. Epoxy molecular weights of about 300 Daltons are generally liquid at room temperature; those of 500 molecular weight are semi-solid, while those of 700 and above are solid in the absence of solvent. Molecular weights much higher than those listed are also used. Epoxy resins also include hybrids such as epoxy alkyds, epoxy acrylics, epoxy silicone, epoxy silane, epoxy polyurethane, epoxy urethanes, and other modifications are also known. In order to reduce the viscosity of these epoxy resins and 2K blends to a typical viscosity for epoxy coating application of around 2000-4000 cps, dilution with a solvent is often needed. Benzyl alcohol is traditionally used to lower viscosity in solvent epoxy applications. This traditionally requires around 10% benzyl alcohol for viscosity reduction of the epoxy coating. An alternative zero volatile organic compound (VOC)-free epoxy viscosity modifier would be advantageous and preferential over benzyl alcohol.
Benzyl alcohol is also used to improve epoxy reactions by compatibilizing the amine hardener and epoxy. This also helps reduce amine blush. In one aspect of the invention, using certain members of a family of distyryl phenol, tristyryl phenol or cumylphenol ethoxylate-based products as additives to epoxy resins without water reduce the viscosity and modify the pot life and cure time as well as reducing or eliminating amine blush. These additives impart no or very low VOCs to the epoxy coating formulation.
Epoxy resins can alternately be dispersed in water to reduce viscosity without adding VOCs. One technical problem that arises is that epoxy resins are rather hydrophobic, and thus do not readily disperse in water. Therefore, surfactants were developed in the past that would disperse these hydrophobic resins in water. These dispersed resins, however, are not freeze/thaw stable.
Waterborne epoxy resins have been in the marketplace for many years. They are widely accepted as environmentally friendly alternatives to solvent-borne or high solids epoxy systems. They offer distinct advantages over solvent-based epoxy coatings for a number of environmental, safety, and health considerations. They have a lower or zero volatile organic compound (VOC) content which reduces their carbon footprint. Lower VOC formulations reduce air pollution and lead to lower odor, improving customer acceptance. Lower VOCs also contribute to decreased flammability and thus improved safety.
Beyond environmental benefits, waterborne epoxy dispersions also provide further technical advantages to the formulator and applicator. The water-based attribute of these epoxy resin dispersions allows water cleanup. Compared to high solids or 100% solids epoxy formulations, they have significantly lower viscosity contributing to ease of use. These water-dispersed epoxy resins can also be produced at higher molecular weight while maintaining low viscosity, improving flexibility over metal as compared to their high solids or 100% solids counterparts. These high molecular weight epoxy resins also improve set time or walk-on time as compared to solvent-based or high solids epoxies due to their ability to “lacquer dry.” The most important applications for water-based epoxy systems today are coatings on concrete, primers for metal and epoxy cement concrete (ECC).
However, one of the problems with low-VOC waterborne epoxy and hardener dispersions is that the freeze/thaw stability of these dispersions is often poor since common anti-freeze solvents such as propylene glycol are VOCs. Another aspect of the instant invention provides a surfactant system comprising ethoxylates of distyrylphenol, tristyrylphenol or cumylphenol that imparts good freeze/thaw stability to epoxy dispersions. In addition, the stability and pot life of the dispersions are improved, without a concomitant extension of the cure time. This is unusual since pot life and cure time cannot usually be improved simultaneously. Gloss and water resistance of the cured coatings were checked and are good.
In addition, these distyrylphenol, tristyrylphenol or cumylphenol-based ethoxylate surfactants allow the preparation of aqueous epoxy resin dispersions that have good long-term stability at room temperature as well as at elevated temperatures. These dispersions are quite stable, retaining consistent viscosity over extended periods. They also impart good freeze/thaw resistance.

These hydrophobes may be converted into surfactants by methods known in the art such as ethoxylation (nonionic), or by ethoxylation followed by either phosphation or sulfonation to produce anionic end groups which in turn can be neutralized resulting in a counterion cation of sodium, potassium or ammonium.
It is known that surfactants such as those listed in U.S. Pat. No. 6,221,934 may be employed to render the epoxy component emulsifiable. These are nonylphenol ethoxylates, alkylphenol initiated poly(oxyethylene) ethanols, alkylphenol initiated poly(oxypropylene)poly(oxyethylene) ethanols, and block copolymers containing an internal poly(oxypropylene) block and two external poly(oxyethylene) ethanol blocks. In this patent, it is explained that these surfactants do not produce good epoxy dispersions for various end use applications. None of these surfactants are known to produce good freeze-thaw properties in epoxy dispersions. No surfactants are mentioned that use distyryl phenol, tristyryl phenol or cumylphenol hydrophobes.
U.S. Pat. No. 6,271,287B1 cites the use of various surfactants employed in epoxy dispersions. These include long-chain alkyl alkali metal sulfosuccinate such as dioctyl sodium sulfosuccinate, sodium lauryl sulfate, sulfosuccinic acid-4-ester with polyethylene glycol dodecyl ether disodium salt, dialkyl disulfonated diphenyloxide disodium salt. None of these surfactants were shown to produce good freeze-thaw properties in epoxy dispersions. None of the surfactants mentioned use distyryl phenol, tristyryl phenol or cumylphenol hydrophobes.
When epoxy dispersions freeze, ice begins to form within the continuous phase. Thereby the continuous phase expands in volume, or, in other words, the emulsion becomes more concentrated. The pressure on the dispersed droplets increases considerably, and the ice crystals can violate the protective surfactant layer around the emulsion particles. This leads to coalescence of the emulsion droplets, destabilization of the dispersion and separation of the water and epoxy, resulting in a poor coating.
It would therefore be an advantage in the art to discover a waterborne epoxy resin with good freeze-thaw stability.
Finally, another of the problems with state-of-the-art hardeners and waterborne epoxy dispersion mixtures used in coatings, adhesives, damping and other products including epoxy cement concrete coatings, coatings for concrete, primers for metal and other applications is that often the pot life (the usable life of a mixture of an epoxy hardener and an epoxy) is correlated strongly to the cure time (time for the applied material to cure). Thus, if the pot life is very long, so is the cure time. However, a long pot life is desired allowing larger batches to be made, while shorter cure times are desired to allow for earlier use of the finished coated product. It is difficult to simultaneously increase pot life while maintaining or decreasing cure time.
There are few options to increase pot life while maintaining or reducing cure time. One such option is to add acetic acid to enhance pot life; this is undesirable since this adds to the VOC (volatile organic compounds) level. VOCs are being reduced or eliminated in current and future coatings formulations. Acetic acid may also add undesired water sensitivity to the final epoxy coating.
It is known that nonyl phenols are used in hardener applications to modify cure time. Nonyl phenols are used in hardeners such as Ancamine 2368 available from Air Products. In epoxy hardener systems, these traditionally are used to increase compatibility with epoxy materials which decreases cure time but also simultaneously decreases pot life, an undesirable combination. These nonyl phenols are also estrogen mimics and are banned for use in coatings and other uses by many countries.
The reaction adduct of 1,3-bis(aminomethyl)cyclohexane (BAC) with ketones is used but produces inconsistent results. Ketimines are the reaction products of ketones and primary aliphatic amines. In the absence of reactive hydrogens, they do not react with epoxy resins. They can be considered blocked amines or latent hardeners, since they are readily hydrolyzed to regenerate the amines. They have low viscosity, long pot lives and cure rapidly when exposed to atmospheric humidity, and are useful in high solids coatings. Unfortunately, these cannot be used in waterborne coatings due to premature unblocking with water. They also contribute to VOCs and require an added step in the formulation of hardeners.
U.S. Pat. No. 6,271,287B1 cites the use of various surfactants employed in epoxy dispersions. These include long-chain alkyl alkali metal sulfosuccinate such as dioctyl sodium sulfosuccinate, sodium lauryl sulfate, sulfosuccinic acid-4-ester with polyethylene glycol dodecyl ether disodium salt, dialkyl disulfonated diphenyloxide disodium salt. None of these surfactants were shown to produce improved combination of long pot life and short cure times. None of the surfactants mentioned use distyryl phenol, tristyryl phenol or cumylphenol hydrophobes.
It would therefore be an advantage in the art to discover an ingredient in a hardener that would simultaneously increase pot life while maintaining or decreasing cure time.
Epoxy thermosets derive their thermal, chemical, and mechanical properties from the highly cross-linked networks. Highly cross-linked epoxy thermosets sometimes suffer from brittleness. Consequently, toughness deficiency is an issue in certain applications. To improve the impact resistance and toughness of epoxy systems, elastomers such as BF Goodrich's CTBN rubbers (carboxyl-terminated butadiene nitrile) are often used as additives or pre-reacted with epoxy resins. Most commonly used products are reaction adducts of liquid epoxy resins (such as DGEBA) with CTBN in concentrations ranging from 5 wt % to 50 wt %. They have been shown to give improved toughness, peel adhesion, and low temperature flexibility over unmodified epoxies.
Primary applications are adhesives for aerospace and automotive and as additives to epoxy vinyl esters for structural composites. Formation of adducts of epoxy resins and carboxylated butadiene-acrylonitrile copolymers (CTBN) is promoted by triphenylphosphine or alkyl phosphonium salts. Other elastomers used to modify epoxies include amine-terminated butadiene nitrile (ATBN), maleated polybutadiene and butadiene-styrene, epoxy-terminated urethane prepolymers, epoxy-terminated polysulfide, epoxy-acrylated urethane, and epoxidized polybutadiene.
A patent by Dow using EO/PO type materials WO 2006/052725 (angres) relates to ambient cure high-solids epoxy resin compositions modified with amphilic polyether block copolymers to increase the fracture resistance or toughness of the cured ambient cure high solids coating composition.
Distyryl phenol, tristyryl phenol or cumylphenol based additives have not been cited in the patent literature or other published literature for use in producing epoxy resin hardeners. These distyryl phenol, tristyryl phenol or cumylphenol based additives have surprisingly been found to improve both the pot life and cure times of epoxy/hardener systems. Pot life can be increased while cure time is maintained or decreased.